How to Install Ponytail for Gemini CLI: Complete Extension Setup Guide

Install Ponytail for Gemini CLI by running gemini extensions install https://github.com/DietrichGebert/ponytail, which registers the extension and makes the /ponytail commands and six specialized skills available in your Gemini sessions.

Ponytail is a Gemini CLI extension that provides "lazy senior dev mode"—a set of always-on rules and commands for code review, technical debt analysis, and over-engineering detection. The extension is packaged as a standard Gemini extension using a manifest file that points to AGENTS.md for core instructions and automatically discovers commands and skills from the repository structure.

Understanding the Ponytail Extension Structure

The extension follows Gemini's standard extension format. At the root of the repository, gemini-extension.json serves as the manifest that registers Ponytail with the CLI.

// gemini-extension.json - defines the extension metadata
{
  "name": "ponytail",
  "version": "1.0.0",
  "description": "Lazy senior dev mode for Gemini CLI",
  "agents": "AGENTS.md"
}

This manifest tells Gemini to load always-on rules from AGENTS.md and automatically discover the commands/ and skills/ directories without additional configuration.

Installation Steps for Gemini CLI

Step 1: Run the Gemini Extensions Install Command

Execute the standard Gemini CLI extension installation command with the repository URL:

gemini extensions install https://github.com/DietrichGebert/ponytail

This pulls the repository, validates the gemini-extension.json manifest, and registers Ponytail as an active extension. The command is documented in the repository's README under the Gemini CLI section (lines 187-194).

Step 2: Alternative Installation for Antigravity CLI

Gemini is being rebranded to Antigravity CLI (agy). The same Ponytail extension works with the new binary using a slightly different command:

agy plugin install https://github.com/DietrichGebert/ponytail

This alternative is documented in the Antigravity CLI subsection (lines 200-206) of the README.

Step 3: Verify the Installation

Start a new Gemini session and test any Ponytail command:

/ponytail lite

A successful installation displays mode confirmation and makes the six Ponytail skills available for the session.

Available Ponytail Commands and Skills

Once installed, Ponytail provides four operating modes via slash commands and six specialized skills:

Operating Modes

Command	Purpose
/ponytail lite	Minimal overhead, essential checks only
/ponytail full	All Ponytail checks enabled
/ponytail ultra	Maximum scrutiny, aggressive flagging
/ponytail off	Disable Ponytail assistance

Built-in Skills

• ponytail — Core lazy-dev assistance
• ponytail-review — Over-engineering detection and review
• ponytail-audit — Code audit and quality assessment
• ponytail-debt — Technical debt identification
• ponytail-gain — Value and improvement analysis
• ponytail-help — Skill documentation and usage help

Invoke skills directly with the skill syntax:

/ponytail-review src/components/Button.tsx

Key Implementation Files

Understanding the source structure helps troubleshoot installation issues:

• gemini-extension.json — Extension manifest defining registration metadata and AGENTS.md reference
• AGENTS.md — Always-on instruction set applied to every Gemini session with Ponytail active
• commands/ — TOML files defining the /ponytail slash commands (lite, full, ultra, off)
• skills/ponytail/ — Implementation of all six Ponytail skills that Gemini autodiscovers

No additional hook files or manual configuration are required—Gemini's extension system handles skill discovery automatically from the skills/ directory.

Common Installation Verification

After installation, confirm all components load correctly:

# Test mode switching

/ponytail full

# Test skill invocation

/ponytail-debt src/

If commands return "unknown command" errors, verify the extension installed successfully with gemini extensions list and re-run the install command if Ponytail does not appear.

Summary

• Install Ponytail for Gemini CLI with gemini extensions install https://github.com/DietrichGebert/ponytail
• Use Antigravity CLI alternative with agy plugin install if running the renamed binary
• Extension manifest at gemini-extension.json registers AGENTS.md rules and autodiscovers skills
• Four modes (lite, full, ultra, off) control Ponytail's assistance level
• Six skills provide specialized code review, audit, debt, and gain analysis capabilities
• No manual configuration required—Gemini loads commands from commands/ and skills from skills/ automatically

Frequently Asked Questions

Does Ponytail work with the new Antigravity CLI?

Yes. The same Ponytail extension is compatible with both gemini and agy binaries. Use gemini extensions install for the original CLI or agy plugin install for the Antigravity rebranded version. Both commands target the same repository URL.

Where are Ponytail's always-on rules defined?

The always-on instructions live in AGENTS.md at the repository root. The gemini-extension.json manifest explicitly references this file, causing Gemini to apply these rules automatically in every session where Ponytail is active—no manual activation needed.

What happens if the gemini extensions install command fails?

Verify you have the latest Gemini CLI version. The extension requires standard Gemini extension support introduced in recent releases. Check gemini extensions list to confirm Ponytail appears; if partially installed, run gemini extensions uninstall ponytail before reinstalling.

Can I use individual Ponytail skills without switching modes?

Yes. Skills like /ponytail-review and /ponytail-debt are directly invocable regardless of the current mode setting. The /ponytail mode commands (lite, full, ultra) primarily control the aggressiveness of always-on behavior and background assistance.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}